1. Field of the Invention
The present invention relates to the field of high speed machining, machine-tools mobile on three axes X, Y and Z, and more particularly to modifications allowing to improve the machining travel of this type of machine.
2. Discussion of the Background
Classically, the tools used in very high speed machining are of the rotary type and are placed at the end of a unique tool-carrying ram mounted moveable along three axes so as to allow machining on a big length, a big width and a big depth, as well as tool exchange, gripping and collection functions in magazines conceived for that purpose.
Generally, these machines comprise several main parts, i.e.:
an actual machining station comprising the tool driven in rotation at the end of the ram and shaping the part to be machined,
a driving station placed near the machining station and constituted by a combination of driving mechanisms ensuring the movements along the axes X, Y, Z of the tool-carrying ram, which also ensures, via an electric spindle, the rotary movement of the tool carried at the end,
a control station collaborating with the driving station according to a pre-established instructions program to ensure and to manage the different machining operations and stages of the different parts to be machined.
The machining station can classically comprise several subsets offering as many additional functions. Thus, for example, a magazine or a tool storage device offers several machining tools to the ram mobile on three axes coming to leave and take the tools, allowing it to ensure as many machining functions as possible on a part to be machined. The machining station can also comprise a device for exchanging parts to be machined managed by the control module and ensuring the exchange between the parts having just been machined and the ones still to be machined.
With the benefit of its experience in the field of high speed machining along three axes and on machines called mono-spindle, the applicant has conceived high precision machines operating at a high velocity capable of achieving high accelerations and rapidity of function in their movement along three axes X, Y and Z by the use of a logical cinematic structure and innovative driving means, well above that achievable by classical machining machines. The applicant has noticed that these machines, even though they have matched the users requirements up until now, can in some situations prove to have limited use in their machining travel. In fact, to reply to the new criteria of acceleration and rapidity of function required for very high speed machining machine-tools, combined with the concern for compactness of the machines, the travels along the three different axes are comprised in intervals defined by the mechanical or geometrical limits of the machine, which intervals can prove to be too short for some applications.
The limitation to the travel is a difficulty often found in the conception of machine-tools and several devices can be found in the prior art, ensuring a movement of the part to be machined so as to enable it to get nearer the tool thus avoiding unnecessary travel and travel times (until the tool is in contact with the part to be machined and begins the machining stage) which would reduce the machine""s performance. Nevertheless, no device has been conceived to enable the lengthening of the machining travel of a machining machine-tool of the type comprising a tool-carrying ram which, ensuring functions of tool gripping, exchange, guidance, and driving moves along three axes X, Y and Z, the three axes forming an orthogonal spatial system of axes and Z being the longitudinal axis of the machine and of which the movements are ensured by linear motors, such as in the case of the machines conceived by the applicant. In fact, the total freedom of movement of the tool-carrying ram combined with its speed due to the use of linear motors, brings new technical criteria and opens a field of possibilities in programming machining on one part to be machined, never previously reached. The existing machine-tools using a tool-carrying ram moving along three axes are, on the whole, less fast and and less precise, and do not have the dynamic constraints of the ones conceived by the applicant, in view of their size, higher travels obtained, or less performing driving means. In addition, the existing devices which ensure the movement of a part to be machined are essential to the following machining stage because the tools of the classical machine-tools do not move parallel to the movements of the part to be machined. Thus, on the axes followed for the movements of the part to be machined, the ram, the headstock and/or the tool-carrying spindle stay fixed.
The applicant has thus studied the concept of an innovative method enabling the widening of the capacities of machines"" machining travel. The difficulty of such a concept is to offer a device enabling to adapt to a machine already answering perfectly to users"" requirements in most applications and for most of the parts to be machined so that it is not built-into the machine to avoid an overload when the device is not necessary. Furthermore, as the increase of the lengths of machining travels of a machine-tool have for direct and known consequence to reduce the velocity of the machine, such a device would be set in motion or would start to function only when the part or the side of the part to be machined (via a machining program) so requires.
In view of this situation and the specifications required, the applicant has carried out research aimed at achieving the aforementioned targets. This research has led to the conception of a method which does not reduce the performance of the basic machining machine-tool, integrable but not built-in to it, and enabling once it has started to function, the machining of parts to be machined which are longer, wider or higher.
According to the main characteristic of the invention, the method for lenghtening the machining travel of a high speed machine-tool of the type comprising a tool-carrying ram ensuring tool gripping, exchange, guidance and driving and moving along three axes X, Y and Z, the three axes forming an orthogonal spatial system of axes and Z being the longitudinal axis of the machine, the movements being ensured by linear motors, is remarkable in that it consists in combining to the machining movements of the tool-carrying ram along one or several axes, one or several rectilinear movements of the part to be machined by parametering and digitizing the relative travels and speeds of the part to be machined with respect to the tool-carrying ram.
This method is particularly advantageous as it enables to lengthen the useful travel of the tool-carrying ram of the machine-tool without reducing the dynamic performances. In fact, the mobility on one or several axes of the part to be machined with respect to the tool-carrying ram already mobile on these three axes enables not only to bring the part to be machined closer to avoid the non machining times and reduce the unecessary travel of the tool-carrying ram, which is what classically occurred in the devices of the prior art but also to reduce these times of bringing closer by moving the tool-carrying ram and the part to be machined along parallel axes but in an opposite way thus reducing dead time.
In this precise application, once the part to be machined and the tool-carrying ram are close, several machining configurations are possible:
either the tool-carrying ram is alone in executing the travel and rotatably driving the tool towards the fixed part to be machined,
or the part to be machined is alone in executing the travel in moving towards the tool-carrying ram fixed with the tool rotatably driven,
or the part to be machined and the tool-carrying ram both move along a parallel direction but in an opposite way.
According to a particularly advantageous characteristic of the invention, this method consists in parametering and digitizing the relative travels and speeds of the part to be machined with respect to the travels on axis Z of the tool-carrying ram. This characteristic is particularly innovative in view of the fact that most machine-tools do not use a tool-carrying ram ensuring a translation on axis Z and they consequently do not ensure the suitability between the translation on axis Z of the tool-carrying ram and a translation parallel with axis Z of the part to be machined in a same direction. This suitability thus requires the mastering of new parameters.
The invention also concerns the device enabling to implement the method for lengthening the machining travel of a high speed machine-tool of the type comprising a tool-carrying ram moving along three axes X, Y and Z, the three axes forming an orthogonal spatial system of axes and Z being the longitudinal axis of the machine, the movements being ensured by linear motors. This device is remarkable in that it comprises inside the machining zone, a part-carrying clamping subset combined with a driving subset ensuring the translation on one or several axes parallel with the axes of the movements of the tool-carring ram, of the part-carrying clamping subset. Furthermore, the driving subset comprises linear motors which drive in translation, synchronising with the movements of the tool-carrying ram on a pair of rails respectively parallel with axes X, Y and Z of the movement of the tool-carrying ram, the part-carrying clamping subset. This consistency in the choice of driving means enables to produce movements of the parts to be machined as fast as the movements of the tool-carrying ram and avoids to penalize the performance of the whole of the machine while ensuring a lengthening of the travels.
Also, contrary to the devices of the prior art, the movement of the part to be machined is not necessary to the functioning of the machine-tool during simple machining thus enabling to leave the part to be machined in fixed position.
The invention also concerns a machining machine-tool adopting the device of the invention. This machine-tool is of the type comprising a machining station, a driving station, a control station, the machining station taking up at least one mobile set for moving or exchanging the parts to be machined of the invention, the mobile set comprising a sealed device isolating the machining station from the outside so as to avoid projections of swarf and is remarkable in that it develops itself around the mobile subset, and thus from its own leaktightness device, an isolating device, linked to its frame, separating the machining station and the elements it is made of from the outside.
This characteristic justifies itself by the new constraints required for the speed of movement during the movements of the parts to be machined. In fact, such devices for exchanging parts or for moving parts to be machined, classically comprises a leaktightness device constituted by a cover and a separating wall which enables to isolate the machining station and to avoid the projection of swarf inside. The movements of the device of the invention have forced the designers to ensure leaktightness of the mobile set with respect to the fixed frame of the machine by rubbing. Therefore, the criteria of speed required for the movements of such a device are such that the rubbing must be limited as far as possible to the detriment of the leaktightness against swarf. Thus, the technological solution of the invention enables to create a second protection around the elements constituting the machining station of the machine-tool so as to avoid the spreading of swarf which would have gone through the first cover or through the first protection. Another advantage of this double protection is that, even though they are protected by their own cover or separating wall, the elements constituting the machining station of the machine-tool and more particularly the lengthening device of the travel of the invention which is a mobile device can work out to be dangerous for any nearby handlers, users or technicians. The presence of this second protection thus enables to answer to the safety at work criteria.
The fundamental concepts of the invention having just been detailed hereinabove in their most elementary form, more details and characteristics will come out more clearly when reading the description hereinafter using as a non limitative and having regard to the attached drawings, a device enabling to implement the method of the invention and of a machine-tool using such a device in accordance with the invention.